1. Field of the Invention
The present invention relates to a method of frame plating and a method of forming a magnetic pole of a thin-film magnetic head through the use of the frame plating.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as areal recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a recording head having an induction-type electromagnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the track width, that is, the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface (medium facing surface) is reduced down to microns or the order of submicron. Semiconductor process techniques are utilized to implement such a structure.
As disclosed in Published Unexamined Japanese Patent Application Heisei 7-262519 (1995), for example, frame plating may be used as a method for fabricating the magnetic poles that define the track width. In this method, an electrode film is formed on the base layer, and a resist layer is formed on the electrode film. This resist layer is patterned through a photolithography process to form a frame to be used for plating. Using this frame, plating is performed through the use of the electrode film previously formed as a seed layer. A plating pattern is thereby formed.
As described above, it has been desired to achieve a thin-film magnetic head having a recording head with a small track width. Therefore, when the magnetic poles are formed by frame plating, it is required to form a plating pattern wherein the pattern width is small while the film thickness is great, and the side walls are nearly orthogonal to the base surface, and part of the sidewalls forming a nearly flat surface has a sufficient height. However, it is difficult in prior art to form such a plating pattern by frame plating because it is difficult to make a resist frame that has inner walls corresponding to the geometry of the above-mentioned plating pattern. This problem will now be described.
The angle between an inner wall of the resist frame and the bottom surface thereof is hereinafter called a rising angle. The height of the part of the inner wall of the resist frame that forms a nearly flat surface is hereinafter called a straight height. It is possible to change the rising angle and the straight height by adjusting the conditions of exposing the resist through the mask pattern, such as the focal point of exposure beams.
If the distance between the base layer and the focal point of the beams above the base layer is increased, the rising angle of the resist frame exceeds 90 degrees while the straight height increases. In contrast, if the distance between the base layer and the focal point of the beams above the base layer is decreased, the rising angle of the resist frame becomes 90 degrees or smaller while the straight height decreases.
In order to obtain a thick plating pattern that does not overhang, it is preferred that the straight height of the resist frame is greater. That is, it is preferred that the rising angle of the resist frame exceeds 90 degrees.
However, in order to control the plating pattern width, it is required to measure the width of the trench of the resist frame from the outer surface of the resist frame (the outer surface of the base layer) before performing plating. The rising angle of the resist frame is required to be 90 degrees or smaller to measure the trench width of the resist frame with accuracy.
As thus described, it is difficult in prior art to achieve both a greater straight height of the resist frame and the rising angle of the resist frame of 90 degrees or smaller. It is therefore difficult to form a thick plating pattern with accuracy in dimensions.
It is an object of the invention to provide a method of frame plating for making a thick plating pattern with accuracy in dimensions, and a method of forming a magnetic pole of a thin-film magnetic head for making the magnetic pole of the head with accuracy.
A method of frame plating of the invention includes the steps of: forming a frame made of a resist such that an inner wall of the frame and a bottom surface thereof form an angle greater than 90 degrees; performing heat treatment on the frame such that the angle becomes 90 degrees or smaller; and forming a plating layer by performing plating through the use of the frame having received the heat treatment.
According to the method of frame plating of the invention, the frame made of a resist is formed such that an inner wall of the frame and the bottom surface thereof form an angle greater than 90 degrees. It is thereby possible to increase the height of a portion of the inner wall of the frame that forms a nearly flat surface. Furthermore, according to the invention, heat treatment is performed on the frame such that the angle becomes 90 degrees or smaller. It is thereby possible to measure the trench width of the frame with accuracy, and to form the plating layer with accuracy in dimensions.
A method of forming a magnetic pole of a thin-film magnetic head of the invention is provided for forming a layer including a magnetic pole portion. The thin-film magnetic head comprises: a medium facing surface that faces toward a recording medium; a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The method includes the steps of: forming a frame made of a resist such that an inner wall of the frame and a bottom surface thereof form an angle greater than 90 degrees; performing heat treatment on the frame such that the angle becomes 90 degrees or smaller; and forming the layer including the pole portion by performing plating through the use of the frame having received the heat treatment.
According to the method of forming a magnetic pole of the invention, the frame made of a resist is formed such that an inner wall of the frame and the bottom surface thereof form an angle greater than 90 degrees. It is thereby possible to increase the height of a portion of the inner wall of the frame that forms a nearly flat surface. Furthermore, according to the invention, heat treatment is performed on the frame such that the angle becomes 90 degrees or smaller. It is thereby possible to measure the trench width of the frame with accuracy, and to form the layer including the pole portion with accuracy in dimensions.
According to the method of frame plating or the method of forming a magnetic pole of the invention, the heat treatment may be performed at a temperature in the range of 70 to 90xc2x0 C. in the step of performing heat treatment.
According to the method of forming a magnetic pole of the invention, the layer including the pole portion may define a track width.
Other and further objects, features and advantages of the invention will appear more fully from the following description.